The present invention relates, in general, to a cargo hold structure for an oil tanker and, more particularly, to a cargo hold structure for an oil tanker, in which instead of mounting a crosstie between longitudinal bulkheads of a cargo hold to support the cargo hold, a vertical web mounted on the longitudinal bulkhead is made wide and a horizontal girder is connected between the vertical webs, thereby controlling the sloshing of a load in the cargo hold and improving the structural strength of the cargo hold.
Generally, a very large crude oil carrier (VLCC) is configured so that a cargo hold is divided into three spaces by means of two longitudinal bulkheads, wherein a reinforcing member such as a crosstie is mounted between vertical webs in order to support the longitudinal bulkheads.
That is, as shown in FIGS. 1 to 3, an oil tanker is configured so that a cargo hold having a closed space is defined by a deck 51, an inner bottom plate 53, and left/right side shells 55, a deck transverse is vertically arranged onto the deck 51 in a horizontal direction of a hull, and a girder 59 is arranged on the inner bottom plate 53 in the horizontal direction of the hull.
In this case, the cargo hold is provided so that an inner space is defined by the longitudinal bulkheads 61 that are vertically arranged in the lengthwise direction of the hull between the deck 51 and the inner bottom plate 53, and the deck 51 and the inner bottom plate 53 are interconnected by a vertical web 63 that is mounted along a width direction of the hull and vertically to the hull. Here, the vertical web 63 is a rectangular reinforcing plate with a width about 0.1 times the total height H of the cargo hold. The vertical webs are arranged at multi-points on the entire face of the longitudinal bulkhead and spaced apart by intervals of a predetermined distance in the lengthwise direction of the hull.
The plurality of vertical webs 63 are interconnected by the plurality of crossties 65 that are horizontally arranged along the width direction of the hull. The crossties 65 also serve as a reinforcing member like the vertical webs 63. Thus, the longitudinal bulkhead 61 can secure a proper structural strength by the vertical webs 63 and the crossties 65 connecting the vertical webs.
Furthermore, the vertical webs 63 are interconnected by a plurality of stiffeners 67, which are horizontally arranged along a lengthwise direction of the hull and have a size relatively smaller than the vertical webs 63. Here, the stiffeners 67 are arranged in a stacked form with certain intervals in the height direction of the hull between the vertical webs 63. Thus, the longitudinal bulkhead 61 can secure a proper structural strength furthermore by the combination of the vertical webs 63, the crossties 65, and the stiffeners 67.
However, in the cargo hold of the conventional oil tanker having the above-mentioned construction, the crosstie 65 is of a heavy structure that is suspended in the space in the cargo hold so as to interconnect the vertical webs 63, so that the crosstie becomes vulnerable to vibrations of the hull and to the sloshing of a load of fluid stored in the cargo hold that takes place as the ship travels.
Further, in the VLCC in which two longitudinal bulkheads 61 divide the inside of the cargo hold, since the structure of the cargo hold may be damaged because of the crossties 65 being connected between the vertical webs 63, the VLCC may be vulnerable to marine safety accidents, and much time and cost are taken when manufacturing the VLCC.
Moreover, according to the rules of Safety Of Life At Sea (SOLAS), a safety device is required that can examine and maintain the safety of the crossties 65 is also needed after delivery of a vessel to a shipowner, so that the manufacturing cost of a vessel problematically increases by even more.